In the days before modern imaging and testing, healers practiced with a principle of nature:

As above, so below

They sought the microcosm in the macrocosm - the fractal nature of how things are designed and function.

Everything follows basic mathematical and natural laws. This gives rise to microsystems.

You will find this same principle in foot reflexology and iridology theories. This is the idea that we can diagnose and treat the whole body using just one part.

Tongue diagnosis falls in alignment with this principle.

In particular, the tongue lets us see all the organ systems broken into 3 levels:

Upper-- Lungs/Respiratory and Heart = Respiratory Microbiome
Middle-- Digestion/Liver = Gut Microbiome
Lower-- Reproductive/Bladder = Urogenital Microbiome

In each area, we are looking for 3 things along a spectrum

Moisture-- Dampness to Dryness
Temperature-- Hot to Cold
Gas Pressure (gasotransmitters)-- Excess/Stagnation/Deficiency

These variables will affect the internal climate and create an ideal terrain for different bacteria, viruses, molds, fungus, etc. to grow and thrive.

This then gives us a diagnosis of what is out of balance and how to MOVE the 3 variables to return the body to the right conditions for the beneficial bacteria/viruses/molds etc to regain healthy control or balance.

For an in-depth explanation check out Dr. Andrew Miles 5 part podcast on Tongue Diagnosis here.